Effect of different rolling amount on the superelastic properties of Cu 70.8 Al 18.6 Mn 10.6 shape memory alloy

Abstract

The objective of this study was to achieve high deformation plastic forming and obtain high comprehensive properties of the Cu-Al-Mn shape memory alloy (SMA) through the investigation of the effects of rolling with gradient deformation and subsequent heat treatment on the microstructure and mechanical properties of a columnar-grained structure Cu_70.8Al_18.6Mn_10.6 SMA. Subsequently, the wedge-shaped alloy samples were quenched after high temperature rolling at 800 and these samples were HR samples, and then the HR samples were heat treated at 800 for 1 h to obtain HR + HT samples. The findings indicate that the HR samples are capable of sustaining a columnar-grain structure even when subjected to high deformation. As the degree of rolling deformation increased, the Vickers hardness of the alloy exhibited a gradual enhancement, accompanied by a corresponding decline in the phase transformation temperature. The HR samples display excellent comprehensive mechanical properties, including high strength, superelasticity and a lower damping coefficient than that of HR + HT samples. The critical stress of martensitic transformation of the alloy increases significantly, from 109 to 276 MPa. In addition, the maximum superelastic strain (ε_SE^Max) of the gradient deformation samples can reach more than 8.5%. Furthermore, these samples can recover more than 90% strain after 12% loading strain. The damping coefficient is maintained at about 0.1. These enhanced properties are primarily attributable to a reduction in the transformation temperature and the formation of a deformed microstructure under conditions of high rolling deformation. The diameter of the recrystallised grains in the HR + HT samples decreased from a value exceeding 1 mm to a value of approximately 200 μm with an increase in rolling deformation. The transformation temperature of the HR + HT samples is higher than that of the HR samples and is essentially aligned with that of the as-cast alloy. The ε_SE^Max of HR + HT samples remain above 5%, and their damping coefficient is close to 0.1, indicating favorable comprehensive properties and reprocessing ability. This study not only offers a novel approach to the synthesis of Cu-Al-Mn SMA but also provides a theoretical and experimental foundation for the utilizations of this high-performance alloy.